The present invention relates generally to zinc-chlorine battery systems and chlorine producing/consuming plants. More particularly the invention relates to an advantageous combination to zinc-chlorine battery stack and a chlorine producing or consuming plant.
Due to the increasing demand for electricity and the decreasing availability (and increasing cost) of distillate oil and natural gas, the need has arisen for an alternate method of supplying peak demand electricity. Presently, the electricity generated for peak demand is supplied from diesel engines and combustion turbines, which are fired by distillate oil and natural gas. One such method is the use of secondary energy storage batteries to store electricity generated from utility baseload facilities during the night or off-peak hours, and discharging these batteries during the hours of peak demand. Secondary energy storage batteries which could be considered for this application include lead-acid, lithium-iron sulfide, sodium sulfur, and zinc-chloride batteries.
The use of secondary energy storage batteries in the above application generally requires a scale up of a basic battery design to form a battery plant capable of delivering electrical energy on the order of several mega-watt hours in a single discharge. One such battery plant design is disclosed in the Whittlesey et al U.S. Pat. No. 4,287,267, issued on Sept. 1, 1981, entitled "Zinc-Chlorine Battery Plant System And Method". This battery system is also described in published reports prepared by the assignee herein, such as "Development of Zinc-Chloride Battery for Utility Applications," Interim Report EM-1417, May 1980, and "Development of the Zinc-Chlorine Battery for Utility Applications," Interim Report EM-1051, April, 1979, both prepared for the Electric Power Research Institute, Palo Alto, Calif. The specific teaching of the aforementioned cited references are incorporated herein by reference.
Although electric utilities will comprise the principal users of "peak-shaving" or "load-leveling" battery plants for service in the sub-transmission network of the utilities, it may be economically advantageous for industrial customers of the electric utilities to also employ battery plants. Due at least in part to the operating and maintenance costs associated with the peak demand generating engines, the electric utilities typically charge a premium or place a surcharge on the electricity supplied to their industrial customers over the peak period. This surcharge is substantial and can amount to several times the normal kilo-watt hour rate charged by the utilities for off-peak electrical energy consumption. Accordingly, industries which consume large amounts of electrical energy may achieve significant savings by employing one or more battery plants to supply or supplement the electricity required during on-peak electrical energy consuming hours.
One industry which is known to require large amounts of electrical power is the "chlor-alkali" industry. This industry refers to the manufacture of chlorine and alkali caustic from electrolytic cells which generate chlorine gas, hydrogen gas and caustic soda from a steady supply of brine electrolytic solution. Banks of these cells are employed in a typical manufacturing plant, and since each cell normally consumes between ten to thirty thousand amperes, the electrical power required to operate a chlor-alkali plant is substantial.
The use of secondary energy storage batteries in the chlor-alkali industry has previously been considered to obtain a more favorable rate structure from the supplying electric utility by permitting the industry to be classified as a disruptable power consuming industry. However, efforts to employ lead-acid batteries for this purpose have not proven to be economically viable. However, the zinc-chloride battery system could also be considered for this purpose since its life-cycle projected cost is more favorable than that for lead-acid batteries. Additionally, the zinc-chloride battery system could be employed in conjunction with the chlor-alkali industry in a "peak shaving" capacity as well.
Accordingly, it is a principal object of the present invention to provide a unique combination of a chlorine producing plant and a portion of the zinc-chloride battery system to yield a low cost energy storage system for the chlor-alkali industry or other chlorine producing industries.
It is a more specific object of the present invention to provide a chlor-alkali plant which combines at least one electrolytic cell and the battery stack and electrolyte circulation subsystems of the zinc-chloride battery system to permit an advantageous transfer of the gas products generated by the electrolytic cell and the zinc-chloride battery stack.
It is an additional object of the present invention to provide a chlor-alkali plant which combines at least one electrolytic cell and the battery stack and electrolyte circulation subsystems of the zinc-chloride battery system to permit the battery stack to supplement the supply of electrical power to the electrolytic cell during the discharging of the battery stack.
It is another principal object of the persent invention to provide a novel combination of a chlorine consuming plant and a portion of the zinc-chloride battery system to yield a low cost energy storage system for chlorine consuming industries.
Additional advantages and features of the present invention will become apparent from a reading of the detailed description of the preferred embodiments which makes reference to the following set of drawings in which: